Synthesis and characterization of Z-scheme In2S3/Ag2CrO4 composites with an enhanced visible-light photocatalytic performance

The low photocatalytic performance of a single photocatalyst mainly originates from a fast recombination of photogenerated charge carriers. Rational design and construction of direct solid-state Z-scheme photocatalysts is an effective approach to improve the charge separation efficiency of photogenerated electron-hole pairs. In this study, a series of Z-scheme In2S3/Ag2CrO4 composite photocatalysts with a different content of In2S3 were synthesized using a facile chemical precipitation method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL) spectroscopy and photoelectrochemical measurements. The photocatalytic activity of the In2S3/Ag2CrO4 composites was evaluated through photodegradation of methyl orange (MO) under visible light irradiation (lambda > 420 nm). The results demonstrate that the optimal Z-scheme In2S3/Ag2CrO4 composite with a theoretical weight content of 4.0% In2S3 provided a photodegradation rate constant for MO of 0.0087 min (-1), which is approximately 2.8 and 5.4 times higher than those of pure In2S3 and Ag2CrO4, respectively. The enhanced photocatalytic activity may be attributed to the formation of a Z-scheme system between In2S3 and Ag2CrO4, effectively prolonging the lifetime of the photoinduced electrons generated by In2S3 and the photoinduced holes generated by Ag2CrO4, which was subsequently confirmed using active species trapping experiments, photoluminescence techniques and photoelectrochemical assays. This work may be useful for rationally designing new types of Z-scheme photocatalysts and provides some illuminating insights into the Z-scheme charge transfer mechanism for application in the solar energy conversion and environmental remediation fields.